The Persian-Median Wars were two conflicts between the dominant Median Empire and its ally the Babylonian Empire against the rising Persian Empire under Cyrus the Great of the Achaemenid dynasty. The first war began in 553 as Cyrus stages a revolt against his relative Astyages of the Medes. Defeating Astyages at the Battle of Pasargadae three years later, Cyrus and the Persians quickly gained the upper hand, defeating the Medes and their Babylonian allies again at the Battle of Bisitun in 549 B.C.

Forced to counter this threat, the Babylonians took over the main leadership of the war as Persian began to move into the Mesopotamian heartlands. At the Battle of Opis in 545 B.C. the Babylonians under Amel-Marduk were successful at defeating a Persian army, restoring momentum to the allied forces. With both the Babylonians and Medians restored by this victory and years of recovery. After the Persians sieged the city of Susa in 543 B.C., the allies counterattacked, breaking the siege and routing the Persians at heavy cost to themselves. With both sides exhausted from over ten years of war and facing threats elsewhere, a peace treaty was signed between the two parties in 542 B.C.

Understanding that the war had weakened his opponents far more than they had weakened his own forces, Cyrus was content to wait for such weariness to take its toll. In 541 B.C. the Babylonian Empire collapsed after a quick succession of weak rulers, splintering into several successor-states, while Media remained weakened and recovering. Seizing the initiative, Cyrus resumed war, conquering Media quickly in 539 B.C. and picking away the Mesopotamian states one by one, completing his campaigns in quick succession by 537 B.C. With both the Medians and Babylonians dealt with, there was relatively little to stop Achaemenid expansion throughout the rest of Asia and Egypt.